共查询到20条相似文献,搜索用时 31 毫秒
1.
The growth of single crystals of lanthanum heptamolybdate is achieved by allowing controlled diffusion of La ions through silica gel using the system La(NO3)3 MoO3 NH4OH HNO3–Na2SiO3. The reaction mechanism leading to the growth is reported. Mechanism of crystallization of La heptamolybdate is discussed. Formation of Liesegang rings consisting of La heptamolybdate crystals in the system is reported. It is observed that concentration programming and seeded growth enhances the size of crystals. The crystals grown in the system are single crystal platelets exhibiting squarish or octagonal facets. Some crystals exhibit a spherulitic morphology. 相似文献
2.
V. V. Kochurikhin K. Shimamura B. M. Epelbaum H. Takeda T. Fukuda 《Crystal Research and Technology》1998,33(1):65-70
The automatic diameter control system using the results of spectral analysis of weight sensor data as a criterion for the amount of feedback tuning was applied successfully for the growth of La3Ga5SiO14 single crystals. The developed method enabled to determine timely the appearance of oscillations in the control system and to adapt the amplification factor automatically for the maintenance of stable crystal shape. Furthermore, the developed system made it possible to estimate the formation of a second phase at a very early stage. 相似文献
3.
Shi-Fu Zhu Jun Liu Bei-Jun Zhao Hong-An Jiang Zheng-Hui Li 《Crystal Research and Technology》1995,30(6):813-816
High quality AgGaSe2 single crystals with 20 mm in diameter and 55 mm in length have been grown by the modified Bridgman technique and the growth habits of AgGaSe2 single crystals have been investigated in detail. It is found that the shape of the growth ampoule affects greatly the nucleation and the growth of AgGaSe2 single crystal. A new cleavage face (101) and the natural faces are observed in the as-grown crystals. For some cases, the growing direction is normal to the (316) face. 相似文献
4.
B. M. Epelbaum K. Shimamura K. Inaba S. Uda V. V. Kochurikhin H. Machida Y. Terada T. Fukuda 《Crystal Research and Technology》1999,34(3):301-309
In spite of their superior laser and polarizer properties rare-earth orthovanadates (REVO4) single crystals have not been adopted yet into extensive industrial applications because of crystal growth difficulties. The main problems of CZ technique are compositional change and diameter instability. This work presents the first attempt to apply the edge-defined film-fed growth (EFG) technique by which well-shaped REVO4crystals have been grown directly. The capillary properties of YVO4 and GdVO4 melt have been measured. The applicability of shaped growth for rare-earth orthovanadate family was approved by successful EFG growth of transparent rod-like macro-defect-free single crystals of YVO4 and GdVO4. We address two main approaches to enhance the quality of EFG crystals: (i) meniscus and crystal shape stability dependence on die top shape and (ii) the strategy of effective operating control. Concave die top was found to be the best choice for high-quality EFG growth of REVO4 along [001] direction. The spectral analysis of weight signal from growing crystal was shown to be a useful feedforward clue to prevent crystallinity degradation at a very early stage. A reasonable stability of the EFG process was achieved using [211], [101], [001] and [100] pulling directions. 相似文献
5.
A. Molchanov U. Hilburger J. Friedrich M. Finkbeiner G. Wehrhan G. Müller 《Crystal Research and Technology》2002,37(1):77-82
Large calcium fluoride (CaF2) single crystals are required for the fabrication of lenses in so‐called wafer‐steppers of future IC‐lithography technologies operating at 193 nm and 157 nm. Numerical simulation plays an important role to design an adequate growth setup and processing conditions for the growth of high quality crystals. An important issue is the consideration of the internal heat transfer by radiation in the semitransparent CaF2 during the crystal growth process. Results of the numerical modeling of the heat transport are presented, which are obtained by using the software package CrysVUn++ with different models considering the internal heat transport in CaF2. To improve the availability of experimental data on CaF2 bulk growth, an especially designed R&D‐facility was built. This growth system is equipped with a variety of in‐situ measurement systems to detect the temperature distributions in the crystal and melt region. Calculated temperature distributions are compared with experimental data. Also first results on single crystal growth will be reported. 相似文献
6.
High-quality single crystals of the high-temperature phase of barium metaborate (α-BaB2O4) up to 100–120 g in weight are grown from a flux in the ternary system BaO-B2O3-Na2O. The growth temperature is below the α → β phase transition temperature. The conditions necessary for growing α-BaB2O4 crystals under metastable conditions are determined and the morphology and optical quality of the crystals grown are investigated. 相似文献
7.
Koichi Watanabe 《Crystal Research and Technology》1995,30(1):49-54
Single crystals of corundum were grown by the top-seeded solution growth technique from a cryolite, Na3AlF6, solvent. The relationship between the growth rate (mg/h) of a crystal and the temperature difference (= supersaturation) or the rotation rate of a seed crystal was investigated, and optimum growth conditions for obtaining single crystals with good quality are discussed. 相似文献
8.
The growth striation of impurity segregation and electrical properties of Ga0.03In0.97Sb single crystals grown by the Czochralski method in an ultrasonic field have been investigated. It is established that ultrasonic
irradiation of the melt during growth significantly decreases the growth striation (in particular, it eliminates striations
spaced at a distance of more than 14 μm). The Ga0.03In0.97Sb single crystals grown in an ultrasonic field had a higher charge-carrier mobility and thermoelectric power in comparison
with the single crystals grown without ultrasound. 相似文献
9.
H. Hilscher 《Crystal Research and Technology》1985,20(10):1351-1361
Studying a number of {101} faces of KDP and DKDP single crystals in the as-grown state we found in most cases one, rarely few, clearly stepped growth hillocks covering the whole face. The geometry of these growth hillocks was determined from photomicrographs; the step heights were measured with a profilometer. To prove our results we carried out X-ray topographic investigations and in-situ observations on KDP crystals. In addition we studied the as-grown faces of ADP and LiJO3 single crystals. 相似文献
10.
H. Kimura T. Numazawa M. Sato V. V. Kochurikhin K. Shimamura T. Fukuda 《Crystal Research and Technology》1996,31(3):301-306
Optical absorption has been measured from 700 to 1300 nm for garnet single crystals by substituting Dy or Ga for Gd or Al of Dy3Ga5O12 grown by the Czochralski method, and a suppression of unstable spiral-shape growth on Dy3Ga5O12 by the substitution was discussed relating the absorption spectra. The total absorption in the single crystals at the wavelength corresponding to the radiation from Ir crucible was decreased relatively with the increase of Gd or Al content. The decrease of this absorption in the single crystals is one of the causes to suppress the unstable spiral-shape growth. 相似文献
11.
The effect of concentration of Mn(II) ions on the growth habit and the surface micromorphology of different as‐grown faces of ammonium oxalate monohydrate (AO) single crystals grown from aqueous solutions was studied at a constant temperature of 30 °C and predefined supersaturations up to 20%. It was observed that the growth habit and the surface morphology of the crystals strongly depend on the supersaturation used for growth and the impurity concentration in the solution. The experimental results were analysed in terms of connected nets determined from different projections of the structure of AO crystals. Analysis of the observations revealed that: (1) the directions of connected nets corresponding to basic growth units composed of single (NH4)2C2O4 · H2O molecules are in excellent agreement with the low‐index crystallographic directions of the orientations of growth layers, (2) all faces appearing in the growth morphology of AO crystals are F faces, and (3) the {001} face growing from pure aqueous solutions is essentially a kinetically rough face but the presence of Mn(II) impurity leads to their appearance in the morphology due to increase in the strength of bonds of the connected nets composing the surface graph. 相似文献
12.
We have designed a double ellipsoid mirror furnace for floating‐zone crystal growth using lamps with rectangular filaments. Its thermal characteristics were studied using an alumina tube for several system configurations. A simple comparison with a commercial furnace that used cylinder lamps for the heating profile was also conducted. By adjusting lamp orientation and positions, one could modify heating profiles easily. In general, the thermal characteristics of the furnace were consistent with the model's prediction [J. Crystal Growth 173 (1997) 561]. The effects of growth chamber and heat pipe were further illustrated. Furthermore, a suitable system configuration leading to better heating uniformity and lower thermal gradients near the growth interface was found for the floating‐zone growth of SrxBa1‐xTiO3 single crystals. 相似文献
13.
N. Pylneva V. Kosyakov A. Yurkin G. Bazarova V. Atuchin A. Kolesnikov E. Trukhanov C. Zilling 《Crystal Research and Technology》2001,36(12):1377-1384
The liquidus surface structure and field of LiB3O5 (LBO) primary crystallization have been revealed in Li2O‐B2O3 ‐MoO3 ternary system. The optimization of charge composition and growth conditions results in large volume optical quality LBO single crystals yielding. Crystallographic properties and real defect structure of grown LBO single crystals have been investigated by X‐ray powder diffraction method and X‐ray reflection topography. The volume of the crystals is partly free of any structural imperfections. 相似文献
14.
Jiecai Han Huaixin Guo Mingfu Zhang Ningning Song Chenghai Xu 《Crystal Research and Technology》2012,47(5):485-490
Nd3+‐doped Y3Al5O12 single crystals have been grown by the horizontal directional solidification (HDS) method in different thermal zone. The Grashof (Gr), Prandtl (Pr), Marangoni (Ma) and Rayleigh (Ra) numbers of melt in HDS system have been discussed for our experimental system to understand the mechanism of melt flow patterns and concentration gradient of dopant. The concentration gradient of Nd3+ ions was explained with melt flow processes during crystal growth in different thermal zone, and results indicated that high growth temperature will be helpful for uniformity of dopant in HDS‐grown single crystal. The main microscopic growth defects such as bubbles and irregular inclusions in HDS‐grown Nd:YAG crystals were observed, and the causes were discussed as well. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
Single crystals of ytterbium tartrate trihydrate have been grown by gel method using silica and agar‐agar gels as media of growth. The medium of growth influences the morphology of grown crystals, silica gel yielding single and polycrystalline in the form of spherulites whereas agar‐agar gel leading to growth of single and twinned crystals. Materials grown as single crystals have been characterized by using optical and scanning electron microscopy (SEM), EDAX, XRD, FT‐IR, CHN and thermogravimetric techniques. The stoichiometry of the grown single crystals is suggested to be Yb(C4H4O6) (C4H5O6).3H2O. The FT‐IR spectrum shows the presence of singly as well as doubly ionized tartrate ligands. Results of thermal analysis indicate that the material is thermally stable up to a temperature of 200 °C. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
The morphology of Zn3P2 single crystals, grown from the vapour phase by sublimation of bulk Zn3P2 in a sealed quartz tube pulled through a high temperature gradient, has been investigated. X-ray diffraction examination showed that the main direction of crystal growth with a tetragonal unit cell is the [021] direction which corresponds to the [111] direction in the pseudocubic system. Transverse and longitudinal cross sections of the single crystals were mechanically polished and chemically etched. Optical examination of the cross sections indicated that the growth of Zn3P2 begins most frequently in the (011) plane. Striae which appeared in a cross section after chemical etching are attributed to the existence of strain fields generated in the sample as a result of temperature fluctuations or as a result of crystal structure defects in the core region. 相似文献
17.
A. Moses Ezhil Raj D. Deva Jayanthi V. Bena Jothy M. Jayachandran C. Sanjeeviraja 《Crystal Research and Technology》2008,43(12):1307-1313
Single crystals of barium oxalate monohydrate (BaC2O4.H2O, BOM) were grown in pure form by controlled diffusion of Ba2+ using the gel technique at different temperatures. Starting from aqueous Ba2+ chloride (BaCl2) and acetic acid (C2H2O4) in gel, this method offers a low‐cost and an easiest alternative to other preparation methods for the production of barium oxalate bulky single crystals. The optimal conditions for the growth of BOM crystals in silica gel were found by investigating different growth parameters such as gel pH, gel aging and crystallization temperature. Irrespective of all such crystallization environments, growth rate of the crystals were initially less and then exhibited supersaturation effect leading to non‐linearity. Gel aging and temperature has profound effect on nucleation density that resulted less number of crystals of maximum size in the gel matrix. Perfect single crystals were grown on gels of higher pH. The macropore morphology and porosity was controlled by changing age of the gel. It has been found that temperature has a fabulous effect in controlling the nucleation density by altering the supersaturation conditions for the formation of critical nuclei. The entire growth kinetics informed that the grown crystals were derived by the one dimensional diffusion controlled process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
The growing of large single crystals of stearic acid (CH3(CH2)16COOH), one of the saturated fatty acids, from organic solutions is reported. There are two parts in this experimental investigation; (1) to clarify the relationship between polymorphism of stearic acid having three modifications, namely, the A-form (orthorhombic), the B- and C-forms (monoclinic) and the growth conditions in the case of solution growth, because this complicated relationship has apparently made it very difficult to obtain large single crystals, (2) to produce large single crystals of stearic acid under the optimum growth conditions according to part (1). As a result large single crystals of stearic acid more than 8 × 8 mm2 in area of the B- and C-modifications were successfully obtained. The values of long spacing, the crystal habit and the cleavage plane are also reported. 相似文献
19.
Relaxor antiferroelectric (Pb,La)(Zr,Sn,Ti)O3 (PLZST) with the composition near the morphotropic phase boundary shows excellent electrical properties. However, the crystal growth of PLZST is limited by the incongruent melting of the materials. Crystal growth of PLZST was induced by a platinum wire in the flux solution with 50 wt% PbO‐PbF2‐B2O3 as a solvent. The obtained PLZST single crystals are optical transparent with light yellow color. The size of the crystals in regular rectangular shape varies from 0.5 mm to 1 mm. The PLZST single crystals exhibit tetragonal phase structure. The element contents of the crystals were measured by inductively coupled plasma atomic emission spectrometry. The results show that the composition of as‐grown crystals is a little bit deviated from the starting composition. The single crystals show two dielectric peaks at 115 °C and 182 °C, corresponding to antiferroelectric‐ferroelectric and ferroelectric‐paraelectric phase transitions. The dielectric data of as‐grown crystals indicate there is typical relaxor behavior near 182 °C. The value of relaxor factor n is 1.49642. 相似文献
20.
V. V. Volkov C. Van Heurck J. Van Landuyt S. Amelinckx E. G. Zhukov E. S. Polulyak V. M. Novotortsev 《Crystal Research and Technology》1993,28(8):1051-1061
The growth features of FeCr2S4 spinel single crystals prepared by chemical vapour transport were studied by means of scanning electron microscopy, transmission electron microscopy, high resolution electron microscopy, electron diffraction and X-ray analysis. Our results indicate that the epitaxial growth of the new phases FeCr7S12 and FeCr8S12, both based on the NiAs structure, can essentially inhibit the growth of large FeCr2S4 spinel single crystals in the octahedral habit. The new phases are fully characterised and the effects of defect ordering in these new phases are also reported. 相似文献